In recent years, magnetic discs such as floppy discs and optical discs such as CD-ROMS have been used as external data record media of computers and data processors. These external data record media store information in the form of digital data.
The digital data recorded on these external data record media are read by prescribed data readers such as magnetic disc driver and CD-ROM driver. Then the data read from the media are applied to the computers or the data processors.
In the conventional recorded data reading system, the data are read at a rated speed defined by each of the record media or the data readers. This is done so that the data can be read at or below a predetermined error rate.
The rated data reading speeds are determined by reflecting an irregularity of data reading accuracy of respective data readers, caused, for example, by a fluctuation of temperature and/or a deterioration of the record media over time.
Thus, in the conventional data reading systems, there is a drawback that the data can not be read at a speed higher than the rated speed provided for the respective system, even when an individual system has a high reading accuracy. Furthermore, there is a serious drawback that the data can not be read accurately at the rated speed if the individual system is seriously deteriorated.